June 15, 2016

Keeping Europe’s longest railway tunnel safe

Written by  Anitra Green
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Swiss Federal Railways (SBB) has adopted a multi-faceted approach to achieve the highest possible level of safety in the new 57km Gotthard base tunnel. Anitra Green reports from Switzerland.

 

A strong focus on safety was evident right from the start of the huge project to build a new Gotthard base tunnel beneath the Swiss Alps. Even at the pre-planning stage, it was clear that a conventional double-track tunnel would not be the right choice for the new tunnel, and it was decided that twin single-track tunnels would be the best option, but with the ability to keep one bore operational at all times.

SBB GBTThe sheer length of the tunnel presented a unique safety challenge, particularly for dealing with accidents and fires which can cause a huge amount of damage and loss of life.
The massive rock overlay of up to 2300m precluded the idea of escape tunnels to the outside world, while an additional service tunnel, similar to that provided for the Channel Tunnel, was ruled out on cost grounds.

The main solution is the provision of illuminated cross-passages every 325m between the twin tubes, protected by fire-proof, airtight doors. That makes 178 cross-passages in all, which not only act as emergency escape routes but also house essential operational and communications equipment.

In addition there are two intermediate crossover points, at Sedrun and Faido, so that trains can switch from one tube to the other. Multifunction emergency stations have been set up at these points in both tunnels, offering a refuge for passengers and an escape route from one tunnel to the other.

Powerful ventilation systems are designed to extract smoke in the case of a fire on a train, and pump in fresh air through vents and side galleries. Should a fire break out in one tunnel, it can be completely closed off so that smoke cannot leak into the other tunnel. Lastly, separate drainage systems have been installed in the two tunnels to carry away any toxic substances.

In parallel with these construction measures, an overall safety concept was developed, with passenger and staff welfare given the highest priority. According to Mr Hans Vogt, SBB's head of safety and quality, SBB had already invested around SFr 100m ($US 103m) in a tunnel safety strategy for its 277 exiting tunnels totaling around 260km. Under this strategy, the first priority is to prevent trains that are not in perfect working order from entering the tunnel. Should a train fail in a tunnel, the defective train must be removed as fast as possible, and there must be suitable infrastructure in place so that people can escape and be rescued from the outside.

For the Gotthard base tunnel, working out the finer details of the safety concept has been the responsibility of SBB's north-south axis project organisation (Pons) task force, headed by Mr Peter Jedelhauser. There are five main pillars to this concept:

  • avoiding accidents
  • containing the damage
  • providing escape routes
  • intervening swiftly, and
  • training personnel.

Avoiding accidents involves detecting in advance any factor that might cause problems. Well before the north and south portals, trains pass under a beam equipped with an array of sophisticated detection equipment to identify a whole range of faults, including overheated axles, blocked brakes, chemical leaks, fire, faulty loading gauge, damaged pantographs, shifting loads, and anything that could represent a hazard. That means faulty trains can be taken out of service before even reaching the tunnel.

If a problem does occur, disruption must be kept to the absolute minimum. "Here, especially, it's important we have two tunnels, one for the 'sick' train and one for the 'healthy' train," Jedelhauser points out. In the case of a fire alarm being activated on board for example, the train stops automatically at the next emergency station and any following trains are also stopped - an essential feature of ETCS Level 2, which is the only train control system used in the tunnel and which all trains have to be equipped with. Then the cause of the alarm is investigated, the train evacuated and the other tunnel cleared if necessary.

Escape routes

Enabling passengers to escape also needed planning. Pictograms showing escape routes are easily visible in the tunnel, emergency stations and cross-passages, and on the trains themselves. Announcements and displays on the trains have been standardised, with older units being retro-fitted to conform. A useful "safety on board" pamphlet in four languages is available.

In the case of a train coming to an unexpected standstill, passengers can find their way to the nearest cross-passage with the help of train staff, backed up by the control centre. There they can walk through to the other tunnel to wait for a relief train to evacuate them. The heavy sliding doors at each end of the emergency cross-passages can be opened and shut even if there is a power failure and are designed to be simple enough even for a child to operate them.

Swift intervention is taken care of by two state-of-the-art fire-fighting and rescue trains acquired at a cost of SFr 40m. They are stationed at each end of the tunnel at the reception and intervention centres set up at Erstfeld and Biasca. Both trains go into action in the case of a fire; they are on standby 24 hours a day, 365 days a year and can leave at five minutes' notice with five people on board. They are expected to be on scene within 45 minutes. Each train consists of two rescue vehicles with facilities for injured passengers, a tank wagon and an equipment vehicle; they can also be divided, allowing the rescue wagons to act independently.

In addition they can call upon reinforcements from local emergency services outside, comprising the police, fire brigade and ambulance services in the cantons of Uri, Ticino and Grisons, which are ready to get to the site of the incident within 30 minutes. All this is organised from the new control centre at Pollegio, responsible for all railway operations in Ticino and the Gotthard route up to Arth-Goldau.

A considerable amount of training has been undertaken to prepare for the opening. A total of 2900 SBB employees and 1000 external associates attended training courses, including drivers of passenger and freight trains as well as staff onboard passenger trains, at a cost of around SFr 25m. To make sure the system works in practice, SBB carried out six exercises between November 2015 and March this year in collaboration with Alptransit Gotthard and the relevant cantons. The final and biggest exercise called for the evacuation of 800 passengers following a fire alarm. A service ICN train continued to the next emergency station at Sedrun, where passengers left the train and walked the 1.5km emergency route to the other tunnel. There they boarded a rescue train which took them to Biasca.

The whole exercise was carried out without a hitch and within the 90 minutes allowed. Jedelhauser was visibly pleased, pointing out that it is essential for the staff to be thoroughly familiar with the new system and actually see the tunnel, in addition to training on the simulator. Both this and the previous exercises, including one with 401 passengers who used the cross-passages to escape to the other tunnel, were a condition set by the Swiss Ministry of Transport (BAV) for granting an operating licence for the Gotthard base tunnel.

In total SBB looked at 700 scenarios involving various incidents and technical defects, 100 of which it analysed in detail. But what if there is an incident in both tunnels simultaneously? "It's extremely unlikely," says Jedelhauser, "but we've also looked at that as a worst-case scenario."

When the Gotthard base tunnel comes into full operation in December this year, a total of 50 to 80 trains a day will be running through the tunnel, including up to five freight trains per hour and direction. Thanks to its careful preparations, SBB has good reason to be confident of having the safest tunnel in the world.

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